1. Field of the Invention
The present invention relates to an optical recording medium, and more particularly, to an optical recording medium having wobbled tracks on which a wobble signal is recorded, an apparatus and method of recording the wobble signal, and an apparatus and method of reproducing the wobble signal.
2. Description of the Related Art
Recordable optical discs such as a Digital Versatile Disc-RAM (DVD-RAM) have concentric or spiral tracks including groove and land tracks. A wobble signal is recorded on the tracks. A track on which the wobble signal is recorded is called a wobbled track. The wobble signal is used in recording an auxiliary clock signal obtaining synchronization information while recording and reproducing information. Hence, the wobble signal has a frequency band that has no impact upon a tracking servo-mechanism provided in a recording and/or reproducing apparatus. The DVD specifications for Rewritable Disc Version 2.0 support a servo band of approximately 3 KHz to radially track and a wobble signal frequency of approximately 157 KHz at standard linear velocity.
User data is recorded on a wobbled track by an optical pickup. To record user data using a laser beam, an optical pickup provided in a recording apparatus and oscillating a recording laser is allowed to move to a desired location. To this end, addressing information used to move the pickup to its desired location is recorded on an optical disc. Here, addressing information refers to identification information assigned for each unit recording block when an information track is divided into a plurality of unit recording blocks.
A representative conventional approach to record addressing information on an optical disc involves recording addressing information on a header region provided separately from tracks on which user data is written. FIG. 1 is a schematic diagram of a conventional optical disc. Referring to FIG. 1, the conventional optical disc has tracks including groove and land tracks where user data can be written, and a header region where header information is recorded in the form of pre-pits. The header region is located at a predefined position in a sector (unit recording block), and addressing information recorded in the header region is used to allow a pick-up device provided in a recording and/or reproducing apparatus to easily move to its desired location. Furthermore, the addressing information can identify information such as a sector number, a sector type, and servo-control information recorded in the header region.
Header information recording supported by the 1999 DVD-RAM standard version 2.0 uses Complementary Allocated Pit Address (CAPA) techniques. According to CAPA techniques, as shown in FIG. 1, header information is recorded in pairs, each pair of information deviating to the right and left of the center of an information track by a half-track.
However, providing an extra header region complicates the fabrication process of an optical disk while requiring an additional circuit to compensate for a wobble signal, since the wobble signal cannot be obtained while a pick-up device passes the header region. Furthermore, in spite of an increased demand for high-density recording media due to the use of multimedia contents, providing an extra header region results in a smaller region in which user data can be recorded.